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United States Department of Agriculture

Agricultural Research Service

Research Project: Genetics, Physiology, and Health Research to Improve Catfish Production

Location: Warmwater Aquaculture Research Unit

Title: Alternative complement pathway of channel catfish Ictalurus punctatus: molecular characterization and expression analysis of factors Bf/C2 and Df

item Zhou, Zunchun
item Liu, Hong
item Liu, Shikai
item Sun, Fanyue
item Peatman, Eric
item Kucuktas, Huseyin
item Kaltenboeck, Ludmilla
item Feng, Tingting
item Zhang, Hao
item Niu, Donghong
item Lu, Jianguo
item Waldbieser, Geoffrey - Geoff
item Liu, Zhanjiang

Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2011
Publication Date: 1/1/2012
Publication URL:
Citation: Zhou, Z., Liu, H., Liu, S., Sun, F., Peatman, E., Kucuktas, H., Kaltenboeck, L., Feng, T., Zhang, H., Niu, D., Lu, J., Waldbieser, G.C., Liu, Z. 2012. Alternative complement pathway of channel catfish Ictalurus punctatus: molecular characterization and expression analysis of factors Bf/C2 and Df. Fish and Shellfish Immunology. 132:186-195.

Interpretive Summary: Commercial catfish producers experience significant losses due to disease in earthen pond culture but molecular mechanisms of catfish immunity are not well understood. The complement system is an important immune defense against microbial pathogens but components of the complement system are not yet characterized. Cooperative research between the USDA, ARS, Catfish Genetics Research Unit and Auburn University led to the identification of three catfish genes that encode complement system proteins. Experimental challenges with a bacterial pathogen showed that gene activity was increased after exposure and implicated these genes in immune responses. This research demonstrated the potential of the genes related to complement factors B and D as markers of fish immune responses.

Technical Abstract: The complement system important in both innate and adaptive host defense against microbial infection in vertebrates. It contains three pathways: the classical, alternative, and lectin pathways. Complement component factors B and D are two crucial proteases in the alternative pathway. In this study, the genes of complement factors Bf/C2 and Df from channel catfish were identified and characterized. Two complement factor B-related genes, Bf/C2A and Bf/C2B, and factor D gene Df were identified. Phylogenetic analysis suggested that Bf/C2A and Bf/C2B is likely orthologous to factor B and factor C2, respectively. Southern blot results suggested that these three genes are all single-copy genes in the catfish genome. The catfish Bf/C2A, Bf/C2B and Df genes were genetically mapped on linkage group 3, 20 and 29, respectively. Bf/C2A and Bf/C2B are highly expressed in liver and kidney, while Df is highly expressed in gill and spleen. After infection with Edwardsiella ictaluri, the expression of Bf/C2A, Bf/C2B and Df genes were found to be remarkably induced in the gill, liver, spleen and kidney at some sampling times, indicating that these three complement factors play a pivotal role in immune responses after the bacterial infection in catfish.

Last Modified: 10/17/2017
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